hopey said:
Look up ohms law. If you are increasing the resistance you wil loose volume. If you want more volume change to 4ohm speakers but these will draw more current. You can experiment with series and parallel circuits if using multiple speakers.
That's not nearly as simplistic as you make it. First, speakers are NOT rated in resistance, they are rated in impedance which is different. SPEAKERS ARE NEVER RATED IN OHMS RESISTANCE, except in the case of DC resistance, which is not a useful spec and virtually never coincides with the impedance rating. Resistance is static whereas impedance is dynamic. Secondly, each speaker driver is entirely unique in it's characteristics and your comments about going from 8ohms to 4ohms will result in more volume seems to suggest a rule that more volume can always be had with lower impedance speakers. This is only true if this change is made between drivers with nothing different except the impedance specfiications... same size, same cone material, same spl specs, same x-max rating, same manufacturer... etc. Yes, some manufacturer do manufacture the same basic driver with the only difference being the impedance but if the OP is replacing an existing driver from a boombox, there is no such animal. Bottom line, the statement that halving the impedance will result in higher volume is only true with the qualifier "with all else being equal" which is the problem since there is no such animal. There will always be differences whether great or small.
Now, from a practical aspect, sensitivity is far more useful specification for predicting loudness/volume. Why? Because doubling the power (or halving it) will only result in a 3 decibel difference in SPL (loudness) levels. It is not uncommon to find speaker drivers ranging from 82 to 100 decibels. A 85db 4-ohm driver will sound no louder than a 88db 8-ohm driver and this is at 1-watt power. A high efficiency 8 ohm driver is always preferable to a low efficiency 4 ohm driver because you can get the same or louder volume with less load, heat and wear/tear on the amplifier (with sensitivity difference of +3-db or greater).
Now, as to your last comment about "experimenting" with parallel and series speakers... why suggest such a thing to someone who might not understand the consequences and results of such actions? How about if he parallels 2 or 3 or 4 (4-ohm drivers)? And with 3.2-ohm drivers being common in boomboxes, how about if he parallels those? Who will pay for his amp if it goes up in smoke?